I tried to add the Apple banana which is a hybrid cultivar of
Musa balbisiana x Musa acuminata 'Silk' http://en.wikipedia.org/wiki/L...
but the system doesn't accept and doesn't allow me to go to step 2. saying : "...don't add quotes around the names....".

Ah never mind! I found out I had a space before the name, that's why the system didn't accept.
When I took that away I got directed to the already existing entry: "Latundan Banana (Musa x paradisiaca 'Silk')" which must be the accepted name.

Hi Myriam,
Thanks for the link to Wikipedia which notes Musa acuminata × M. balbisiana (AAB Group) 'Silk'.
According to Grin this hybrid cross has the botanical name Musa x paradisiaca.
So we have cultivar 'Silk'. You would type Silk into the cultivar field without quotes because the system will add them.
I've added it. Apple Banana (Musa x paradisiaca 'Silk')